1. Field of the Invention
The present invention relates to a power supply device using a magneto AC generator and a method of controlling the power supply device.
2. Description of the Related Art
As a power supply device, there are conventionally known, for example, power supply devices each using a magneto AC generator disclosed in JP 4931987 B or JP 5008749 B. Such power supply device generally includes a magneto AC generator, a rectifier circuit, and a generated voltage control circuit. Electric power generated by the magneto AC generator is converted into a DC by the rectifier circuit, and then input to the generated voltage control circuit. The generated voltage control circuit performs short-circuit control so as to obtain a voltage in accordance with, for example, a voltage of an electrical load including an electrical storage device, to thereby supply the electric power to the electrical load.
However, the conventional technologies have the following problems.
In the conventional power supply device using the magneto AC generator, the generated voltage of a generator alone is controlled in accordance with the voltage of the electrical load. For this reason, the generator is required to generate electric power with a single generated voltage. Meanwhile, in the magneto AC generator, a generated voltage by which power generation efficiency becomes the maximum differs depending on rpm of a rotor. Therefore, the generator of the conventional power supply device does not necessarily generate electric power with the generated voltage by which the power generation efficiency becomes excellent.
Further, in the generated voltage control circuit, electric power supply to the electrical load is controlled only in accordance with a state of the electrical load. However, in the case of a motor that includes a power supply device mounted thereon, for example, a state of a torque supplying device (engine in a case of automobile) for a generator varies constantly. Therefore, even in a case where the torque supplying device is operated with high load and low efficiency, power generation is performed only in accordance with the state of the electrical load, which is inefficient.
On the other hand, in the magneto AC generator, the amount of generated power differs depending on the rpm of the rotor. The magneto AC generator of the conventional power supply device therefore does not always perform power generation necessary for the electrical load.
In order to solve the problems described above, a rectifier circuit and a short circuit provided at an output terminal of the magneto AC generator are switched in accordance with an operating state of the rotor or the torque supplying device, to thereby reduce input torque and improve power generation efficiency. In the case of switching to the short circuit, however, the input torque can be reduced but the power generation cannot be performed at all. Further, when the rectifier circuit and the short circuit are switched, the torque changes abruptly, resulting in deterioration in ride quality in the case of a vehicle.
For the improved power generation efficiency, the generated voltage is switched for each rpm range so as to use a range having high power generation efficiency. However, the input voltage is classified on an rpm range basis, and hence electric power cannot be always generated with the highest efficiency. Further, the DC voltage transformer does not have a boost function, and hence, when a voltage for obtaining the highest efficiency is equal to or lower than an output voltage, electric power cannot be generated with the highest efficiency, and the amount of generated power is reduced.